This invention pertains to an external testing system and more particularly to an external pipe testing system utilizing hydraulic blowout preventor rams in a pipe test configuration.
Various tools have been developed for externally testing a pipe joint connection particularly for use with oil well pipe or tubing. As the drilling of oil wells has become more expensive due to increased costs and the hazardous conditions that exist in many current drilling operations, the need for such testing has increased. In drilling operations, the need to leak-proof connections is amplified by such factors as cost of drilling and environmental considerations. For the most part, in recent years the depth of drilling has increased on the average well and this generally means as increase in the pressures encountered. As pressures increase so do the opportunities for leaks in casing, tubing, and snubbing operations and for washouts in drill pipe tool joints. Such leaks can cause lost production time, drilling delays, costly repairs, injury to workers etc.
In a snubbing operations, a string of pipe is forced into a wellbore under pressure, for example, to remove an obstruction in the well, to inject fluids into a well, etc. Blowout preventors are used to seal around the pipe being inserted into the wellbore to prevent any pressurized fluid from escaping around the outside of the string of pipe. The body of individual segments of pipe comprising the string of pipe to be snubbed are usually rack-tested prior to use to make sure that there are no leaks in the body of the pipe. However, as the connections between the various pipe sections are madeup and snubbed into the well, they are usually immediately subjected to high external pressures. The previously described rack testing will not detect a leak that exists in the pipe joint connections between pipe sections. Such a leak creates very hazardous working conditions at the well site in that high pressure fluid may flow from inside the wellbore through a leak in the pipe to the interior of the pipe and upwardly through the string of pipe being snubbed into the well. If such a leak occurs, regardless of danger to workers, such pipe leak must be corrected, which is an expensive operation when the leak occurs downhole.
In workover operations, many times an obstruction in the well has caused high pressures to be confined to a lower section of the wellbore. When a tool on the end of a pipe string breaks through such an obstruction, the entire string of pipe is subjected to the well pressure which can be of a high magnitude. Such fluid under pressure will find leaks in the pipe and be transmitted to the surface through the pipe string.
Another use for pipe testing occurs prior to drill stem testing, which relies on the integrity of the pipe string to test the pressure of a formation. If a drill pipe is leaking, it is not known whether the formation pressure is depleting or the pipe is leaking. Pipe leaks can also cause tool joint washouts which can be an expensive condition to correct.
Various external pipe testing systems have been used with varying degrees of success. Many such systems are bulky and cumbersome and thus are unsuitable for use in the limited space available at the wellhead when pipe is being inserted into a wellbore. Those devices which are hinged to wrap around the pipe often fall into this category. Other systems do not lend themselves to speed of operation, particularly where the testing is performed as the pipe is being run into an oil or gas well. Still others may not be effective in sealing completely and effectively to hold such seal under high pressures. Systems which pertain directly to the general type of pipe testing that is the subject of this application are shown in U.S. Pat. Nos. 3,034,339; 3,478,577; 3,713,521; 3,871,209; 3,921,437; 4,010,633; 4,136,552; and 4,152,926. Other testing systems which involve blowout prevention type apparatus used as such are shown in U.S. Pat. Nos. 3,872,713 and 4,090,395. None of these patents however utilize blowout preventor type devices in a test configuration such as disclosed in this application.
These prior devices each incorporate features which render them less than desirable for the general use of this technique in many instances. Many are complicated to manufacture and maintain. Some are cumbersome to use and thus undesirable because of the time and difficulty associated with their use. Because of the importance of testing pipe on a more universal basis it is desirable to provide an inexpensive simple system which is easy and fast to use and economically justifiable for general use.
It is therefore an object of the present invention to provide a new and improved external pipe testing system which is economical to manufacture, simple to use and maintain, and uncumbersome and fast to operate at the wellhead.